What could cause a swollen labia and nausea?

Majora or minora: Nausea is usually not associated with labia disease or conditions other than pregnancy or incarcerated hernia in the labia majora. The first can be evaluated with a drugstore pregnancy test. The latter requires emergency treatment. Many conditions can cause swollen labia such as trauma, tumor, cysts, infection, allergy, varicoeles, and more. See your gynecologist to be sure.